Thin rotary-fiberized glass insulation and process for producing same

ABSTRACT

A method of forming a needled rotary fiberglass glass insulation product is provided. The formation of the needled insulation product may be conducted in a continuous in-line process in which the fibers are rotary formed, a binder is sprayed onto the hot fibers, the fibers are collected onto a conveyor and formed into a fiberglass pack, the fiberglass pack is passed through the oven, and the cured insulation blanket is passed through a needling apparatus. The reduction in thickness and increased density caused by the needling process permits the production of lower thickness and higher density insulation products. In particular, the needled insulation product may have a thickness of less than about 0.75 inches and a density from about 1 pcf to about 10 pcf. The needled insulation product may be utilized in household appliances, water heaters, and HVAC equipment.

CROSS REFERENCE TO RELATED APPLICATIONS

The application is a divisional of U.S. patent application Ser. No.11/179,174 entitled “This Rotary-Fiberized Glass Insulation And ProcessFor Producing Same” filed Jul. 12, 2005, the entire content of which isexpressly incorporated herein by reference.

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION

The present invention relates generally to rotary fiberglass insulationand more particularly to a needled, bindered rotary-fiberized glassinsulation product that has a reduced thickness.

BACKGROUND OF THE INVENTION

Conventional fibers are useful in a variety of applications includingreinforcements, textiles, and acoustical and thermal insulationmaterials. The fibers can be formed from molten organic materials suchas polymers or inorganic materials such as glass. Short, straight fiberstypical of conventional thermal and acoustical insulation materials aremade by rotary fiberizing techniques and are interconnected by binders.In such techniques, a molten glass material is delivered to a spinner.Fibers produced by the rotating spinner are drawn downwardly towards aconveyor by a blower. As the fibers move downward, binder is sprayedonto the fibers and the fibers are collected into a high loft,continuous blanket on the conveyor. The blanket is passed through acuring oven and the binder is cured to set the blanket to a desiredthickness. Because of its combination of thermal, acoustical, andmechanical properties and low cost, rotary fiberglass is the preferredinsulation for many applications, including HVAC equipment, waterheaters, ranges, and other household appliances where the requiredthickness is greater than one inch.

In most conventional gas-fired water heaters, the air intake for thecombustion chamber and the combustion chamber containing the burner toheat the water tank are located at or near floor level. However, in somecircumstances, flammable liquids such as gasoline, kerosene, organicsolvent based paint and cleaning supplies may be located near the gaswater heater. Vapors from these combustible liquids may accumulate onthe floor of the room and some vapors may be drawn into the combustionchamber and ignited by the pilot flame or the flame within thecombustion chamber, causing a backflash. The flames could spreadoutwardly from the water heater and ignite any flammable material withinits path. As a result of the occurrences of water heater fires, manysafety standards require that the air flow intakes of gas water heatersbe located about 18 inches or more above the floor to reduce or preventthe intake of combustible vapors into the combustion chamber.

Specific examples of attempts to raise the air flow intakes above theground are set forth below.

U.S. Pat. No. 4,940,042 Moore, Jr. et al., which discloses a directventing system for an indoor water heater that vents the combustionchamber of the water heater directly with the outdoor atmosphere. Aconduit assembly extends from an indoor end attached to the water heater(such as to the top) to an outdoor end in communication with the outsideatmosphere. The conduit assembly is external to the water heater. Theconduit provides continuous combustion air inlet and flue gas outletplenums to isolate the combustion chamber of the water heater from theindoor room air.

U.S. Pat. No. 5,697,330 to Yetman et al., which. describes apower-vented water heater that includes a draft inducer fan attached tothe top end of the storage tank of the water heater via a molded plasticadapter. The molded external plastic adapter has an inlet to receive hotgas from the combustion chamber and cooling external air and an outletfor discharging the received gas. A combustion gas discharge pipe isconnected to the fan outlet, and an air intake pipe that has a firstportion connected to the outlet leg of the adapter to deliver combustiongas and a second portion coupled to the burner inlet to delivercombustion air along with gaseous fuel.

U.S. Pat. No. 6,058,892 to Haak, II, which describes an air flow controland routing apparatus for attaching to a gas water heater to restrictentry of floor-level gases into the water heater. The air flow controlapparatus includes an skirt for surrounding the base of the water heaterand an external air intake tube attached to the skirt for transportinginlet air to the combustion chamber. The air intake tube is preferablylocated at least three feet from the floor, or halfway up the waterheater.

U.S. Patent Publication No. 2002/0134322 to Dolan, which describes asafety device for preventing the ignition of flammable vapors by theopen flames within a gas fired water heater. In one embodiment of theinvention, the combustion chamber is enclosed in a barrier skirt and anexternal “snorkel” is attached to the side of the water heater such thatthe air intake is above the floor. The snorkel is preferably 18 inchesin length.

Although such prior art systems each have a device or apparatus formoving the air intake above the ground, the systems require additionalequipment, such as pipes, fans, adapters, and the like, that arepositioned external to the water heater. Not only does such equipmentraise the overall cost of the water heater, but it also creates a waterheater that requires a larger amount of storage space.

In certain applications, a thinner insulation product is desired orrequired. In these particular applications, rotary formed fiberglass istypically not used because without expensive modifications to the rotaryfiberizing manufacturing line, the rotary fiberglass insulation blanketcannot be controlled to a thickness below one inch. In order to producean insulation product less than about one inch, and especially less thanabout ½ inch thick, a more expensive insulation such as flame attenuatedor needled E-glass insulation is typically used.

Needle punching, or “needling”, is a method commonly used to bondnon-woven, carded, or air-laid blankets without the use of chemicalbinders. In the needle punching process, barbed needles are passed inand out of the blankets to entangle the fibers. However, needling acarded or air-laid blanket of rotary glass fibers is difficult becausethe carding or air-laid process breaks the fibers into short lengthsthat are insufficient for mechanical bonding. As a result, a second typeof fiber, such as E-glass, polyester, nylon, or aramid, isconventionally added to the rotary glass fibers. These additional fibersadd significant cost to the final product as the second fiber is moreexpensive than the rotary glass fibers.

Thus, there exists a need in the art for a thin rotary fiberglassinsulation product that is inexpensive to manufacture, that can beformed using existing manufacturing lines, and that may be used inapplications where a thin insulation is desired.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a needled rotaryfiberglass insulation product that has a reduced thickness. Theinsulation product is formed of single component rotary glass fibers atleast partially coated with a binder. Suitable binders include aphenol-formaldehyde binder, a urea-formaldehyde binder, a polycarboxylicbased binder, a polyacrylic acid glycerol (PAG) binder, or a polyacrylicacid triethanolamine (PAT binder). Preferably, the binder is desirably alow formaldehyde or formaldehyde-free binder composition. The glassfibers may have a diameter from about 2 to about 9 microns and a lengthof from about ¼ of an inch to about 4 inches. The small diameter of theglass fibers and the needling of the insulation as described below helpgive the final insulation product a soft feel and flexibility. Inaddition, the needled insulation product may have a compressed overallaverage thickness of about 0.1 inch to about 0.75 inch, preferably fromabout 0.25 to about 0.50 inches, and a density of from about 1 pcf toabout 10 pcf, preferably from about 3 to about 5 pcf. The thin, needledrotary fiberized insulation product is useful in a variety of thermaland acoustical applications, such as appliance insulation, HVACequipment, water heaters, and acoustical panels.

It is another object of the invention to provide a method of forming aneedled rotary fiber insulation product that has a thickness of about0.75 inches or less, preferably less than about 0.5 inches. Theinsulation product may be formed in a continuous in-line process inwhich single component rotary glass fibers are formed, a binder issprayed onto the hot fibers, and the binder coated fibers are collectedonto a conveyor and formed into an insulation pack. The insulation packis then passed through a curing oven to cure the binder and form aninsulation blanket. To reduce the thickness of the insulation blanketand increase the density, the insulation blanket is passed through aneedling apparatus. The thickness and density of the final insulationproduct may be controlled by controlling how fast the insulation blanketmoves through the needling apparatus, the strokes per minute of theneedling apparatus, the number and types of needles used, and/or thedegree of penetration of the needles into the insulation blanket. Theneedled, thin fiberglass insulation product may be rolled onto a creelby a roll-up device for shipping or for storage for use at a later time.Alternatively, the needled insulation product may be fed directly into adie press, cut into individual parts having a predetermined size and/orshape, and packaged.

Another object of the present invention is to provide a water heaterthat utilizes the rotary glass fiber insulation product of the instantinvention. The water heater contains air flow intakes that penetrate theouter walls of the water heater to permit air external to the waterheater into the water heater and into the combustion chamber. An airflow passageway is positioned along the outer edge of the water heaterbetween the outer wall of the water heater and the rotary glassinsulation product of the present invention. The reduced thicknessprovided by the rotary glass insulation product enables the formation ofthe airflow passageways in the hot water heater. The air flowpassageways connect the air intakes and the combustion chamber so thatoxygen is provided to ignite the burner. In preferred embodiments, theair flow intakes are located about 18 inches or more above the floor.The air flow intakes may be flush with the outer walls of the waterheater or they may jut outwards from the outer walls of the waterheater. A barrier layer may optionally be positioned on the needledinsulation product to act as a fire retardant. The barrier layer may beformed of foil or another suitable fire retardant material and may beaffixed by conventional methods known by those of skill in the art.

It is an advantage that the needled insulation product is flexible dueto the combination of chemical bonding from the binder and mechanicalbonding from the needling process.

It is also an advantage of the invention that the thin insulationproducts made in accordance with the present invention can bemanufactured using current manufacturing lines, thereby saving time andmoney.

It is another advantage of the invention that by needling the glassfiber insulation product a softer feel is provided.

It is a further advantage of the present invention that the needledinsulation product has a low k value that is equivalent to or less thanconventional thick rotary fiberized glass insulation blankets.

It is also an advantage of the present invention that the needledinsulation product is easy to work due with to its reduced thickness andflexibility.

The foregoing and other objects, features, and advantages of theinvention will appear more fully hereinafter from a consideration of thedetailed description that follows, in conjunction with the accompanyingsheets of drawings. It is to be expressly understood, however, that thedrawings are for illustrative purposes and are not to be construed asdefining the limits of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of this invention will be apparent upon consideration ofthe following detailed disclosure of the invention, especially whentaken in conjunction with the accompanying drawings wherein:

FIG. 1 is an elevational view of a manufacturing line for producing aneedled rotary fiberglass insulation product according to at least oneexemplary embodiment of the present invention; and

FIG. 2 is a partial cross-section of a water heater utilizing a needledrotary fiberglass insulation product in accordance with at least oneother exemplary embodiment of the present invention.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS OF THE INVENTION

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, the preferred methodsand materials are described herein. All references cited herein,including published or corresponding U.S. or foreign patentapplications, issued U.S. or foreign patents, or any other references,are each incorporated by reference in their entireties, including alldata, tables, figures, and text presented in the cited references. It isto be noted that the phrase “binder composition” and “binder” may beused interchangeably herein.

In the drawings, the thickness of the lines, layers, and regions may beexaggerated for clarity. It will be understood that when an element suchas a layer, region, substrate, or panel is referred to as being “on”another element, it can be directly on the other element or interveningelements may also be present. Also, when an element is referred to asbeing “adjacent” to another element, the element may be directlyadjacent to the other element or intervening elements may be present.The terms “top”, “bottom”, “side”, and the like are used herein for thepurpose of explanation only. It is to be noted that like numbers foundthroughout the figures denote like elements.

The present invention relates to rotary fiber insulation products thathave a reduced thickness, preferably a thickness of about 0.75 inches orless, and a method of forming such rotary fiber insulation products. Thethin fiberglass insulation is produced by needling a thick, loftyinsulation product to increase the density and reduce the thickness ofthe insulation. The thin insulation product is useful in a variety ofthermal and acoustical applications, such as, appliance insulation, HVACequipment, water heaters, and acoustical panels.

The manufacture of the thin fibrous insulation product according to thepresent invention may be carried out in a continuous process byfiberizing molten glass, spraying binder onto the fibers, forming asingle component fibrous glass insulation pack on a moving conveyor,curing the binder on the fibrous glass insulation pack to form aninsulation blanket, and needling the insulation blanket. Turning to FIG.1, glass may be melted in a tank (not shown) and supplied to a fiberforming device such as a fiberizing spinner 15. The spinners 15 arerotated at high speeds. Centrifugal force causes the molten glass topass through the holes in the circumferential sidewalls of thefiberizing spinners 15 to form glass fibers. Single component glassfibers of random lengths may be attenuated from the fiberizing spinners15 and blown generally downwardly, that is, generally perpendicular tothe plane of the spinners 15, by blowers 20 positioned within a formingchamber 25. Examples of glass fibers that may be utilized in the presentinvention are described in U.S. Pat. No. 6,527,014 to Aubourg; U.S. Pat.No. 5,932,499 to Xu et al.; U.S. Pat. No. 5,523,264 to Mattison; andU.S. Pat. No. 5,055,428 to Porter, the contents of which areincorporated by reference in their entirety.

The blowers 20 turn the fibers downward to form a veil or curtain 30.The glass fibers may have a diameter from about 2 to about 9 microns andmay have a length of from about ¼ of an inch to about 4 inches.Preferably, the glass fibers have a diameter of from about 3 to about 6microns and a length of from about ½ of an inch to about 1½ inches. Thesmall diameter of the glass fibers and the needling of the insulation asdescribed below helps give the final insulation product a soft feel andflexibility.

The glass fibers, while in transit in the forming chamber 25 and whilestill hot from the drawing operation, are sprayed with an aqueous bindercomposition by suitable spray applicators 35 so as to result in adistribution of the binder composition throughout the formed insulationpack 40. Water may also be applied to the glass fibers in the formingchamber 25, such as by spraying, prior to the application of the bindercomposition to at least partially cool the glass fibers. Although anyconventional binder such as phenol-formaldehyde and urea-formaldehydemay be used, the binder is desirably a low formaldehyde bindercomposition, such as a polycarboxylic based binder, a polyacrylic acidglycerol (PAG) binder, or a polyacrylic acid triethanolamine (PATbinder). Suitable polycarboxy binder compositions for use in the instantinvention include a polycarboxy polymer, a crosslinking agent, and,optionally, a catalyst. Such binders are known for use in connectionwith rotary fiberglass insulation. Examples of such binder technologyare found in U.S. Pat. Nos. 5,318,990 to Straus; 5,340,868 to Straus etal.; 5,661,213 to Arkens et al.; 6,274,661 to Chen et al.; 6,699,945 toChen et al.; and 6,884,849 to Chen et al., each of which is expresslyincorporated entirely by reference. The binder may be present in anamount of from less than or equal to about 10% by weight, and preferablyin an amount less than or equal to about 3% by weight of the totalproduct. The low amount of binder contributes to the flexibility of thefinal insulation product.

The glass fibers having the uncured resinous binder adhered thereto maybe gathered and formed into an uncured insulation pack 40 on an endlessforming conveyor 45 within the forming chamber 25 with the aid of avacuum (not shown) drawn through the insulation pack 40 from below theforming conveyor 45. The residual heat from the glass fibers and theflow of air through the insulation pack 40 during the forming operationare generally sufficient to volatilize a majority of the water from thebinder before the glass fibers exit the forming chamber 25, therebyleaving the remaining components of the binder on the fibers as aviscous or semi-viscous high-solids liquid.

The coated insulation pack 40, which is in a compressed state due to theflow of air through the pack 40 in the forming chamber 25, is thentransferred out of the forming chamber 25 under exit roller 50 to atransfer zone 55 where the insulation pack 40 vertically expands due tothe resiliency of the glass fibers. The expanded insulation pack 40 isthen heated, such as by conveying the pack 40 through a curing oven 60where heated air is blown through the insulation pack 40 to evaporateany remaining water in the binder, cure the binder, and rigidly bond thefibers together. Heated air is forced though a fan 75 through the loweroven conveyor 70, the insulation pack 40, the upper oven conveyor 65,and out of the curing oven 60 through an exhaust apparatus 80. The curedbinder imparts strength and resiliency to the insulation blanket 10. Itis to be appreciated that the drying and curing of the binder may becarried out in either one or two different steps. The two stage processis commonly known as B-staging.

Also, in the curing oven 60, the insulation pack 40 may be compressed byupper and lower foraminous oven conveyors 65, 70 to form a fibrousinsulation blanket 10. It is to be appreciated that the insulationblanket 10 has an upper surface and a lower surface. The upper and loweroven conveyors 65, 70 may be used to compress the insulation pack 40 togive the insulation blanket 10 a predetermined thickness. The curingoven 60 may be operated at a temperature from about 200° C. to about325° C. Preferably, the temperature of the curing oven ranges from about250° C. to about 300° C. The insulation pack 40 may remain within theoven for a period of time sufficient to crosslink (cure) the binder andform the insulation blanket 10. In particular, the insulation pack 40may remain in the oven 60 for about 30 seconds to about 3 minutes, andpreferably for about 45 seconds to about 1½ minutes to cure the binder.The insulation blanket 10 exiting the curing oven 60 may have a densityof from about 0.3 pcf to about 4.0 pcf and a thickness from about 1 toabout 12 inches.

After the binder is cured, the insulation blanket 10 is subjected to aneedling process in which barbed needles 85 are pushed in a downward andupward motion through the fibers of the insulation blanket 10 toentangle or intertwine the fibers and impart mechanical strength andintegrity to the insulation blanket 10. Needling the insulation blanket10 also increases the density and reduces the overall thickness of theblanket 10. The needling process or needle punching may take place withor without precursor step of lubricating. In addition, the needlingprocess may occur in a needling apparatus 95. A needling apparatus 95such as may be utilized in the instant invention may include a webfeeding mechanism, a needle beam with a needleboard, needles, such as,for example, ranging in number from about 500 per meter to about 10,000per meter of machine width, a stripper plate, a bed plate, and a take-upmechanism. Rollers may also be provided to move the insulation blanket10 through the needling apparatus 95 during the needling process and/orto compress the lofted insulation blanket 10 prior to the blanket 10entering the needling apparatus 95.

The needles 85 are typically secured within the needling apparatus 95 toa vertically reciprocating needle board. Each of the needles may includeone or more downwardly or upwardly pointing barbs. Alternatively, theneedles 85 may have a forked tip. Other configurations of needles 85that would grab and entangle the fibers are also considered to be withinthe purview of the invention. Depending on the configuration of thebarbs on the needles 85, the fibers may become entangled on either theupward or downward stroke of the needles 85. For example, the barbs orforks on the needles 85 may capture and push individual fibers as theneedles 85 move in the downward stroke, thereby entangling theindividual fibers with adjacent fibers. As the needles 85 move upwardlyout of the insulation blanket 10, the fibers slip off the barbs andremain entangled in the collection of fibers forming the needledinsulation product 100. It is to be appreciated that the insulationblanket 10 may be needled from one or both sides, for example, on itsupper surface, on its lower surface, or on both surfaces.

Prior to needling, the majority of the fibers in the insulation blanket10 are oriented in a generally horizontal orientation. After needling,some of the horizontally oriented fibers are placed in a generallyvertical orientation. This change in fiber orientation mechanicallybonds the fibers and gives the needled insulation product 100 rigidityand stiffness. In addition, the needling process and mechanical bondingof the fibers allows for improved control over the thickness of theneedled insulation product 100. Controlling the thickness of theinsulation product 100 may facilitate the installation of the finalinsulation product 100 into its desired application. For example, byneedling the insulation blanket 10 to a desired thickness, there may beno need to physically compress the needled insulation product 100 duringits installation because it already has the desired thickness for thespace or area in which it is to be installed.

The needles 85 may be pushed in and out of the insulation blanket atabout 100 to about 1500 strokes per minute. The needles 85 may have agauge (size) in the range of from about 9 to about 43 gauge and mayrange in length from about 3 to about 4 inches. The needling apparatus95 may include needles having the same size, or, alternatively, acombination of different sized needles may be included. The punchdensity is preferably about 5 to about 100 punches per squarecentimeter. The punching depth or degree of penetration of the needles85 through the insulation blanket 10 and into the bedplate of theneedling apparatus 95 is preferably from about 0.25 to about 0.75 incheswhen needling from one side.

After passage throughout the needling apparatus 95, the needledinsulation product 100 may be rolled by a roll-up device 90 for shippingor for storage for use at a later time, as depicted in FIG. 1. Thus, theformation of the needled insulation product 100 may be conducted in acontinuous in-line process in which the fibers are formed, binder issprayed onto the hot fibers, the fibers are collected onto a conveyorand formed into an insulation pack, the insulation pack is passedthrough the oven to cure the binder and form an insulation blanket, andthe insulation blanket is passed through the needling apparatus androlled onto a creel as described in detail above. Alternatively, theneedling insulation product may be fed directly into a die press and cutinto individual parts, which may then be packaged.

Although the needling of the insulation blanket is highly suitable forin-line manufacturing processes, needling of the insulation blanket mayalso occur in an off-line process in which the cured insulation blanketis packaged, such as in rolls, for either shipping or storage. Therolled insulation blanket (not shown in the figures) may then be takenseparately to a needling apparatus for needling as described above.Preferably, needling is conducted in-line.

The needled insulation product 100 may have a compressed overall averagethickness of about 0.1 inch to about 0.75 inch, preferably from about0.25 to about 0.50 inches, and a density of from about 1 pcf to about 10pcf, preferably from about 3 to about 5 pcf. The thickness and densityof the final insulation product 100 may be controlled by controlling howfast the insulation blanket 10 moves through the needling apparatus 95,the strokes per minute of the needling apparatus 95, the number ofneedles 85, the type of needles 85, and the degree of penetration of theneedles 85 into the insulation blanket 10. The reduction in thicknessand increased density caused by the needling process permits theproduction of lower thickness and higher density final insulationproducts 100.

Needling also assists in providing a softer feel to the final insulationproduct 100. One particular advantage brought about by needling theinsulation blanket 10 is that needling the insulation blanket 10 allowsfor the production of a final insulation product 100 that has adecreased thickness and a higher density (such as over about 3 pcf).Moreover, needling higher loft, lower density insulation blankets 10 todensify the blanket 10 using mechanical bonding according to at leastone aspect of the instant invention is less expensive to manufacturethan forming a higher density, thin, rotary-fiberized insulation productwithout needling, which requires costly equipment. It is also lessexpensive than competing needled E-glass and flame attenuated insulationproducts. Thus, thin insulation products 100 made in accordance with thepresent invention can be manufactured using current manufacturing lines,thereby saving time and money. Further, the needle punched rotaryprocess of the present invention permits the production of products witha wider range of densities than that which is currently available withneedled E-glass insulation.

The needled insulation product 100 may be used as an insulative materialin household appliances and various other acoustical applications. Forinstance, the needled insulation product 100 may be used in householdappliances (such as ovens, ranges, and microwave ovens), hot waterheaters, dishwashers, HVAC equipment, and acoustical panels. Oneparticularly advantageous use for the thin insulation material 100 is asinsulation for hot water heaters. The thin insulation product 100 may beused to provide an internal air intake chamber and raise the air intakeabove the ground. Such internal air passageways eliminates the need forthe external piping and other equipment required by the prior art.

An exemplary embodiment utilizing the needled insulation product 100 ina hot water heater 120 is illustrated in partial cross-section in FIG.2. FIG. 2 depicts air flow intakes 135 penetrating the outer wall 110.The air flow intakes 135 are in fluid communication with the air flowpassageways 150, which, in turn, are in fluid communication with thecombustion chamber 125. The air flow intakes are located a distance “X”from the floor (F). It is to be appreciated that although FIG. 2 depictstwo air flow passageways 150, one air flow passageway or more than twoairflow passageways are also considered to be within the purview of thisinvention. The airflow passageways 150 are positioned along the outeredge of the water heater 120 between the outer wall 110 of the waterheater 120 and the needled insulation product 100 to provide the oxygenneeded to ignite the burner 130 positioned in the combustion chamber 125and produce a flame to heat the water stored in the internal water tank(not shown in FIG. 2). In preferred embodiments, the air flow intakes135 are located 18 inches or more above the floor (F) to be incompliance with current safety standards as discussed above. Air flowintakes 135 may be flush with the outer wall 110 of the water heater asdepicted in FIG. 2, or, alternatively, they may jut outwards from theouter walls of the water heater 120 (not shown), such as in the form ofa tube or pipe. A barrier layer 140 may optionally be positioned on theneedled insulation product 100 to act as a fire retardant. The barrierlayer 140 may be formed of foil or another suitable fire retardantmaterial and may be affixed by conventional methods known by those ofskill in the art.

The needled insulation product 100 enables the formation of the airflowpassageways 150 in the hot water heater 120 due to the reduced thicknessprovided by the insulation product 100. Also, the needled insulationproduct 100 is easier to work with than conventional lofty insulationdue to its reduced thickness and flexibility. Further, the needledinsulation product 100 is less expensive to produce than conventionalalternative insulative materials. In addition, the thin insulationproduct 100 has a low thermal conductivity (k value) that is equivalentto or less than the thick insulation blankets currently used in homeappliances. As a result, the insulative properties of the needledinsulation product 100 are equivalent to, or better than, current loftyinsulation.

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples illustrated belowwhich are provided for purposes of illustration only and are notintended to be all inclusive or limiting unless otherwise specified.

EXAMPLE Needled Rotary Glass Fiber Insulation

Single component glass was melted and rotary-fiberized in a unit withmultiple spinners. The hot fibers were sprayed with a polyacrylic acidglycerol (PAG) binder, the fibers were collected on a conveyor, andformed into an insulation pack. The insulation pack was then passedthrough a curing oven for a sufficient amount of time and at asufficient temperature to cure the binder and form an insulationblanket. The average fiber diameter was 5.9 microns, the PAG bindercontent was 1.64% by weight of the total insulation blanket, the averagedensity of the insulation blanket was 1.01 lb/cu ft, and the averagethickness of the insulation blanket was 1.1 inches. The nominal thermalconductivity (k-value) at 300° F. was determined to be 0.51 Btu-in/hr-sqft-F.

The insulation blanket was then needled to increase the average densityand reduce the average thickness. A single-sided needling apparatus with36 gauge needles was used. The line speed was set at 30 ft/min, thepunch frequency was 600 strokes/min, the punch density was 14.4punches/sq cm, and the punch depth was 0.25 inches into the bedplate.The final average density of the needled insulation blanket (needledinsulation product) was determined to be 3.12 lb/cu ft, the finalaverage thickness was 0.33 inches, and the thermal conductivity(k-value) at 300° F. was 0.34 Btu-in/hr-sq ft-F.

The needled insulation blanket (needled insulation product) was facedwith an aluminum foil/fiberglass scrim facing. Water heater insulationparts were then die-cut from the faced, needled insulation product.

The invention of this application has been described above bothgenerically and with regard to specific embodiments. Although theinvention has been set forth in what is believed to be the preferredembodiments, a wide variety of alternatives known to those of skill inthe art can be selected within the generic disclosure. The invention isnot otherwise limited, except for the recitation of the claims set forthbelow.

1.-7. (canceled)
 8. A method of forming a needled rotary glassinsulation product having a reduced thickness comprising the steps of:rotary-fiberizing single component glass fibers to form single componentglass fibers having random lengths; applying a binder to at least aportion of said glass fibers; collecting said at least partially coatedglass fibers to form an insulation pack; passing said insulation packthrough an oven to at least partially cure said binder on said glassfibers and form an insulation blanket; and needling said insulationblanket to a predetermined thickness to form said needled rotary glassinsulation product.
 9. The method of claim 8, further comprising thestep of: blowing said glass fibers downward to form a veil of saidfibers prior to applying said binder to said glass fibers.
 10. Themethod of claim 8, wherein said needling step comprises: pushing needlesin a downward and upward motion through said insulation blanket toentangle said glass fibers and impart mechanical strength and integrityto said insulation blanket.
 11. The method of claim 8, furthercomprising the step of: compressing said fiberglass pack in said ovenbetween upper and lower compression rollers prior to needling saidinsulation blanket.
 12. The method of claim 11, further comprising thestep of: rolling said needled rotary glass insulation product onto acreel for shipping or storage.
 13. The method of claim 11, furthercomprising the steps of: cutting said needled insulation product into apredetermined shape; and packaging said cut insulation product forshipping or storage.
 14. The method of claim 8, wherein saidpredetermined thickness is a thickness of less than or equal to about0.75 inches. 15-20. (canceled)
 21. The method of claim 14, wherein saidpredetermined thickness is from about 0.25 inches to about 0.5 inches.22. The method of claim 14, wherein said needled rotary glass insulationproduct has a density from about 1 pcf to about 10 pcf.
 23. The methodof claim 22, wherein said needled rotary glass insulation product has adensity from about 3 pcf to about 5 pcf.
 24. The method of claim 8,wherein said binder is at least one member selected from the groupconsisting of a polycarboxylic based binder, a polyacrylic acid glycerolbinder and a polyacrylic acid triethanolamine binder.
 25. The method ofclaim 24, wherein said binder is present on said single component rotaryglass fibers in an amount less than or equal to 3% by weight of saidneedled rotary glass insulation product.
 26. The method of claim 22,further comprising positioning a fire-retarding barrier layer on saidneedled rotary glass insulation product.
 27. The method of claim 22,wherein said single component glass fibers have a diameter from about 2to about 9 microns and a length from about 0.25 to about 4 inches.
 28. Amethod of forming a fire-retardant, needled rotary glass insulationproduct having a reduced thickness comprising the steps of:rotary-fiberizing single component glass fibers to form single componentglass fibers having random lengths; applying a binder to at least aportion of said glass fibers; collecting said at least partially coatedglass fibers to form an insulation pack; passing said insulation packthrough an oven to at least partially cure said binder on said glassfibers and form an insulation blanket; needling said insulation blanketto a predetermined thickness to form said needled rotary glassinsulation product; and positioning a fire-retarding barrier layer onsaid needled rotary glass insulation product.
 29. The method of claim28, wherein said predetermined thickness is a thickness less than orequal to about 0.75 inches.
 30. The method of claim 29, wherein saidpredetermined thickness is from about 0.25 inches to about 0.5 inches.31. The method of claim 28, wherein said needled rotary glass insulationproduct has a density from about 1 pcf to about 10 pcf.
 32. The methodof claim 28, wherein said single component glass fibers have a diameterfrom about 2 to about 9 microns and a length from about 0.25 to about 4inches.
 33. The method of claim 28, wherein said binder is at least onemember selected from the group consisting of a polycarboxylic basedbinder, a polyacrylic acid glycerol binder and a polyacrylic acidtriethanolamine binder.